Beam compass

ABSTRACT

A trammel head assembly, characterized by the provision of improved locking means for rigidly locking the trammel body to a scale upon which it is slidably mounted. More particularly, the means for locking the trammel body to the triangular scale comprises a yoke member having a transverse portion extending longitudinally completely through said opening, and a pair of parallel leg portions that extend integrally from the ends of said transverse portion within corresponding grooves contained in the ends of said trammel body. Screw means connected with said body are arranged to engage the ends of said leg portions to laterally displace said yoke means in a locking direction relative to the scale.

United States Patent [72] Inventor Miquel Angel Rivera Colon 625 ArticoSL, Puerto Nuevo, PR. 00920 [211 App]. No. 868,994 [22] Filed Oct. 24,1969 [45] Patented June 29, 197] [54] BEAM COMPASS 7 Claims, 4 DrawingFigs.

[52] US. Cl 33/27 [5| Int. CL t B43l 9/04 [50] Field oISearch 33/27 (C),158. 159, 160. I73 [56] References Cited UNITED STATES PATENTS 365,0316/l887 Trout 33/158 648,576 5/1900 Taylor 33/158 Primary Examiner-Leonard Forman Assistant Examiner-Charles E. PhillipsAttorney-Scrivener, Parker, Scrivener and Clarke engage the ends of saidleg portions to laterally displace said yoke means in a lockingdirection relative to the scale.

PATENTED JUH29l97l 3,589,013

6, lmml 26 INVENTOR MIGUEL ANGEL RIVERA COLON BEAM COMPASS As evidencedby the US patents to Hansdorfer No. 447,642 and Nelson No. 1,219,141, itis known in the patented prior art to provide dividers or scribing meansof the trammel type including a trammel head that is mounted for slidingmovement upon a scale or ruler. Furthermore, as shown by the Zurcher US.Pat. No. 2,974,416, it is known to provide trammel apparatus of the typereferred to above that is adapted for use with a triangular scale. Thepresent invention was developed to provide an improved trammel headespecially designed for use in connection with a triangular scale of thetype having a longitudinal groove in each of the three scale faces.

The primary object of the present invention is to provide an improvedtrammel head having an opening for slidably receiving a triangularscale, and locking means for locking the head to the scale. Theinvention is characterized in that the locking means includes a yokehaving a transverse portion that ex tends longitudinally through theopening, and parallel leg portions that are slidably guided in verticalgrooves contained in the ends of the body, respectively. Screw means areprovided for displacing said yoke in the locking direction to force thetransverse portion into the corresponding groove in the scale, the yokebeing accurately guided by the grooves in which the yoke leg portionsare received.

A more specific object of the invention is to provide a trammel head ofthe type described above, wherein the yoke means has a U-shapedconfiguration, the ends of the yoke leg portions including inwardlydirected stop projections that limit the extent of downward movement ofthe yoke in the locking direction. The screw means for displacing theyoke in the locking direction include a screw member secured at one endwith the trammel body between the ends of and parallel with the yoke legportions, and a nut member threadably connected with the screw means andadapted to engage the ends of the yoke leg portions for displacing theyoke in the locking direction.

Other objects and advantages of the invention will become apparent froma study of the following specification when viewed in the light of theaccompanying drawing, in which:

FIGS. 1 and 2 are exploded and end elevation views, respectively, of thetrammel body;

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2; and

FIG. 4 is a perspective view illustrating a pair of trammel headsmounted on a triangular scale or rule.

Referring now to the drawing, the trammel head 2 includes a triangularbody 4 having a triangular opening 6 for slidably receiving a triangularscale 8 in any ofits three l20-displaced positions of orientation.Secured at one end to and extending downwardly from the apex portion ofthe trammel body is a selected scribe means (such as a pin 10 or apencil 12, as shown in FIG. 4). Referring to FIG. 3, the pin 10 has athreaded upper shank portion that is secured in a correspond ing bore inthe lower apex portion of the trammel body. When not in use, the pin maybe enclosed by a protective removable cover 14.

in accordance with the present invention, improved means are providedfor locking the trammel body at a selected position on the scale. Tothis end, yoke means 18 are provided having a transverse portion 18athat extends longitudinally through the body opening 6, and a pair ofparallel leg portions 18b, 18c integral with the ends of said transverseportion. The leg portions are slidably received in correspondingvertical grooves 4b, 4c, respectively, contained in the ends of trammelbody 4 intermediate the upper apices thereof, whereby the yoke 18 isaccurately guided in the vertical plane containing the scribe means 10as shown in FIG. 2. At their upper ends. the leg portions 18b and 18:are provided with inwardly directed top projections 180' that limit thedownward extent of movement ofthe yoke means in the locking direction.

On each of the three faces of the triangular scale 8 is provided alongitudinal groove 20 as is conventional in the art. in

order to displace the yoke means downwardly to force the transverseportion 18a into frictional locking engagement with the adjacent groove20, screw means are provided that include a vertical screw member 22secured at its lower end to the central upper portion of body 4 betweenthe yoke leg portions 18b and 18c, said screw member extending upwardlyand having threadably connected thereto a knurled nut 26 the lowersurface of which is adapted to engage the upper surfaces of the freeextremities of the leg portions 118k and 180. Thus when the scale isassembled within the body opening 6 and the nut 26 is tightened todisplace the yoke 18 downwardly, the rounded lower extremity of thetransverse portion 18a is forced within the longitudinal groove 20 tofrictionally lock the trammel to the scale.

In order to permit accurate positioning of the trammel head on thescale, preferably the body 4 is formed of a transparent material (suchas a suitable synthetic plastic material) and is provided on each of thewall surfaces ofthe triangular opening 6 with indicia lines 30 that arevisible when the trammel head is assembled on the scale. While the yokeand nut members may be formed of any suitable rigid metallic ornonmetallic material, preferably these components are also formed of asuitable transparent synthetic plastic: material. The scale 8, which isa conventional drafting scale commonly used by architects, draftsmen andengineers, normally has a length of 6, l2, 18 or 24 inches and isgenerally formed of metal, wood or a synthetic plastic material.

To use the trammel apparatus as a beam compass, the trammel bodycarrying the pin 10 is adjusted to a position opposite the zero indiciaon the selected scale, whereupon the righthand trammel body ispositioned at a given spaced distance as indicated by the desired scaleindicia visible therethrough. Following tightening of the nuts tofunctionally lock the trammel bodies to the scale, the pencil l2 andscale 8 can be swung in an are about the pin 10.

While in accordance with the provisions of the Patent Statutes thepreferred form and embodiment of the invention has been illustrated anddescribed, it will be apparent to those skilled in the art that variouschanges and modifications may be made in the apparatus described withoutdeviating from the inventive concept.

What I claim is:

l. A trammel head adapted for concentric slidable mounting upon a scale,comprising a trammel body containing an opening for receiving a scale;

and means for releasably locking said trammel body to said scale,comprising a yoke member having a transverse portion extendinglongitudinally completely through said opening, and a pair of parallelleg portions each of which is integral at one end with opposite endsofsaid transverse portion, respectively, said leg portions beingslidably received in parallel-opposed grooves contained in said trammelbody, respectively, and screw means cooperating with the other ends ofsaid leg portions for effecting coplanar displacement of said yokemember in a locking direction to effect frictional locking engagementbetween said transverse portion and said scale. 2. A trammel head asdefined in claim 1, wherein said yoke member is generally U-shaped andincludes adjacent the extremities of said leg portions on the adjacentsurfaces thereof inwardly directed projection means adapted to cooperatewith the external surfaces of said body member to limit the extent ofmovement of said yoke member in the locking direction.

3. A trammel head as defined in claim 2, wherein the opening containedin the trammel body is generally triangular, and further wherein thelateral surface of the transverse portion of said yoke member remotefrom said trammel body is rounded for locking cooperation within acorresponding longitudinal groove contained between two apices of atriangular scale.

4. A trammel head as defined in claim 2, wherein said screw meanscomprises a screw member coplanar with both said trammel body and saidyoke member, said screw member being connected at one end with saidtrammel body and extending outwardly from the external surface thereofparallel with and arranged between said leg portions, and a nut memberthreadably connected with said screw member and arranged for engagementwith the extremities of said leg portions to displace said yoke memberin the locking direction.

5. A trammel head as defined in claim 4, wherein said trammel body isgenerally triangular and includes external surfaces generally parallelwith the corresponding wall surfaces of said triangular opening.

6. A trammel head assembly as defined in claim 5, wherein said trammelbody includes scribe means contained in the plane of and extendingoutwardly from one apex portion of said body, and further wherein saidyoke means, said screw member and said scribe means are contained in avertical central plane that extends midway between the other two apicesof said trammel body.

7. Trammel apparatus including, in combination,

a triangular scale including in each of the three faces thereof a grooveextending longitudinally substantially the full length thereof;

a trammel head mounted for sliding movement on said scale, said headincluding a triangular body containing a triangular openingcorresponding with the cross-sectional configuration of and slidablyreceiving said scale; and

means for locking said trammel head to said scale, comprising a yokehaving a transverse portion extending longitudinally through saidopening, and a pair ofleg portions integral with the ends ofsaidtransverse portion and slidably received in corresponding parallelgrooves contained in the ends of said body, respectively, and screwmeans con nected with said body for cooperation with said leg portionsto displace said yoke in a direction to force said transverse yokeportion into function-locked engagement with the corresponding groove issaid scale.

1. A trammel head adapted for concentric slidable mounting upon a scale,comprising a trammel body containing an opening for receiving a scale;and means for releasably locking said trammel body to said scale,comprising a yoke member having a transverse poRtion extendinglongitudinally completely through said opening, and a pair of parallelleg portions each of which is integral at one end with opposite ends ofsaid transverse portion, respectively, said leg portions being slidablyreceived in parallel-opposed grooves contained in said trammel body,respectively, and screw means cooperating with the other ends of saidleg portions for effecting coplanar displacement of said yoke member ina locking direction to effect frictional locking engagement between saidtransverse portion and said scale.
 2. A trammel head as defined in claim1, wherein said yoke member is generally U-shaped and includes adjacentthe extremities of said leg portions on the adjacent surfaces thereofinwardly directed projection means adapted to cooperate with theexternal surfaces of said body member to limit the extent of movement ofsaid yoke member in the locking direction.
 3. A trammel head as definedin claim 2, wherein the opening contained in the trammel body isgenerally triangular, and further wherein the lateral surface of thetransverse portion of said yoke member remote from said trammel body isrounded for locking cooperation within a corresponding longitudinalgroove contained between two apices of a triangular scale.
 4. A trammelhead as defined in claim 2, wherein said screw means comprises a screwmember coplanar with both said trammel body and said yoke member, saidscrew member being connected at one end with said trammel body andextending outwardly from the external surface thereof parallel with andarranged between said leg portions, and a nut member threadablyconnected with said screw member and arranged for engagement with theextremities of said leg portions to displace said yoke member in thelocking direction.
 5. A trammel head as defined in claim 4, wherein saidtrammel body is generally triangular and includes external surfacesgenerally parallel with the corresponding wall surfaces of saidtriangular opening.
 6. A trammel head assembly as defined in claim 5,wherein said trammel body includes scribe means contained in the planeof and extending outwardly from one apex portion of said body, andfurther wherein said yoke means, said screw member and said scribe meansare contained in a vertical central plane that extends midway betweenthe other two apices of said trammel body.
 7. Trammel apparatusincluding, in combination, a triangular scale including in each of thethree faces thereof a groove extending longitudinally substantially thefull length thereof; a trammel head mounted for sliding movement on saidscale, said head including a triangular body containing a triangularopening corresponding with the cross-sectional configuration of andslidably receiving said scale; and means for locking said trammel headto said scale, comprising a yoke having a transverse portion extendinglongitudinally through said opening, and a pair of leg portions integralwith the ends of said transverse portion and slidably received incorresponding parallel grooves contained in the ends of said body,respectively, and screw means connected with said body for cooperationwith said leg portions to displace said yoke in a direction to forcesaid transverse yoke portion into function-locked engagement with thecorresponding groove is said scale.